The present invention relates to a piston for internal-combustion engines, and more particularly, to a piston for an internal-combustion engine comprising essentially circular cylinder liners, a piston bottom and a piston shaft closed at least along a portion of its axial length in the circumferential direction with pin eyes set back with respect to the diameter of the piston shaft, and mutually opposite webs between the pin eyes and the shaft wall.
DE 41 09 160 C2 shows a known piston constructed asymmetrically with respect to the pin axis in order to achieve a high elasticity while utilizing the lightweight construction and in order to avoid a stress concentration. The pulled-down portion of the shaft wall extends along a larger angle at the circumference than the pulled down portion of the shaft wall of the counter-pressure side. Curved webs extend respectively between the shaft wall and the indented pin eyes. The webs are displaced to the outside relative to the counter-pressure side on the pressure side of the piston. The entire piston construction is mirror-symmetrical with respect to a plane perpendicular to the pin axis.
It is an object of the present invention to develop a piston for internal-combustion engines such that it has a bottom surface which is easily accessible for a cooling, high stabilities and sufficient rigidity and can be manufactured by conventional processes in an easy manner and at reasonable cost. This piston is suitable for high to very high compressions and very high engine powers with the combustion space and piston temperatures being correspondingly high.
According to the present invention, this object has been achieved by providing that the piston is forged, and arranged in the internal-combustion engine to be splash oil cooled, one of the webs between the one pin eye and the shaft wall is displaced outwardly relative to the opposite web applied to the one pin eye, and the two webs of the other pin eye are spaced equidistantly from a center plane perpendicularly to a pin axis.
By producing the piston as a forged component, a high-strength, highly loadable, stiff piston is constructed by processes known per se. A good elimination of heat becomes possible by using a splash oil cooling which acts upon the piston bottom. By displacing one of the webs between the pin eye and the shaft wall toward the outside, a good accessibility of the piston bottom is permitted for the oil splash. When the splash oil cooling and the corresponding bore is arranged in one of the bearing seats of the crankshaft, this web which is displaced to the outside is situated above the corresponding bore.
By replacement of the web, a relatively large bottom surface for the splash oil cooling is made available. Moreover, the displacement of the web toward the outside permits a free accessibility of the oil splash without any impairment of the stability or rigidity of the piston. The one-sided displacement of one of the webs permits maintenance of relatively large shaped-out areas as a result of which a forging operation becomes possible without any excess wear.
The rigidity and the stability of the piston are advantageously increased, in accordance with the present invention because the webs not placed to the outside are connected with the pin eye in a center area of the latter. This arrangement results in geometrically favorable conditions on the pin eye which, on the one hand, permit in a simple manner a connection required for the stability and, on the other hand, permit almost balanced lever conditions on the pin eye.
With respect to the rigidity and stability of the piston, it is advantageous for the webs to extend almost in a straight line inasmuch as a result, the spring effect because of the shaping is avoided.
For the rigidity and stability of the piston, it is also advantageous to lead the webs away from the pin eye approximately at a right angle, that is, at an angle of between approximately 80 and 100 degrees.
With a view to a frictional output which is as low as possible, it is advantageous for pulled-down shaft sections to extend between the pin eye which lead away from the closed piston shaft and which permit a sufficient guiding of the piston.